Tire measuring device



Oct. 17, 1950 G. VAN 1. wEs'roN 2,526,056

" TIRE MEASURING DEVICE Y Filed Nov. 27, 1945 Patented ct. i7,

'UN I TED S TT PAT EN T FF ECE 2,526,056 v rin-n MEA'SURING Device frrittv'aii IfWst Ridg'eeld, Conn., assignor toUnitedfStatesRubber Company, New York, N. Y., a'corpora'ti'n of New `e'rsey f Appicatnliiieimr 27,1945, serial'No. 631,164

-1 clarin. (C1. 334-172) This invention rclates to-aneXtremely apparatus for 'measuring the diameter f 'the tread of tires in the plane of the wheel. I

The larger trucks and buses'now traveling'the highways are commonly v`provided Vwith dual tires that is two pneumatic tires foreach rear wheel. It isfextremely important that the'two tires ior the same Wheel when properly inli'atedshall'have the same diameter, for if one of the'r'dual tires `isonly half an inch larger indiameter than the other, it will carry by far the f greater #portion of the load upon that Av vllrleenlkand asa result will be subjected to excessive wear since it carries most of the load which should be `borne equally hy the two tires. r x 'The 'importance of matching dual ytires as to size has been stressed heretofore, 'and it has'been proposed to lus'e atire "diameter caliper adapted to spanthe tire and measure its size, but itis very dilcult forA oneA person alonev to measure `the diameter of a tire with a caliper lbecause of the length of the same required to span a large tire. Furthermore the inner dual tire is more or less inaccessible, and in the case of buses both tires may be covered by a fender which prevents the use of such a caliper.

Itx'ha's also been proposed 'heretofore to .jack up a wheel ofthe vehicle equipped with dual tires and determine the size of each tire on that wheel by placing a steel tape around the periphery of the tread of one tire to measure its circumference, `and then similarly measure the circumference of the other tire to determine how closely they are matched as to size, but this is a dicult and time consumingT measuring operation.

The present invention contemplates an extremely simple and practical tire measuring device whereby the diameter of a tire maybe de-v Fig. 4`is a rear-view of a right rear truck or g bus wheel equipped with dual tires, and showing the tire measuring device of thepreslent invention in position to 'measure the size of the outer The present measuring device as 'shown the drawing comprises fan elongated body .lil having twofspaced Hired tire engaging points and a scale graduated to give tire diameter readings, land a lever Il` having a tread engaging point at one end and a pointer at its other end. This ylever is adapted to be pivoted to one end of the body lil so that its pointer will travel over the scale disposed at the other end of the body.

The body I0 shown in the drawing is lmade hollow so that the pointer arm portion of the stood from the following description when readl Y lever Il may swing within the hollow casing vformed by the body. This body IB is so constructed that it has along one curved edge two spaced xed tire engaging points I2 and I3 and it is narrow at one end to which the lever il is pivoted and wide at the other end so that this wide end will receive the relatively long curved scale I4 which is graduated to give tire diameter readings throughout the range of from 28 inches fto 48 inches. This body I0 is conveniently formed of the side walls l5 and I6 of plywood that are maintained in spaced relation to each other by the spacing blocks, Il, I8, I9 and 20, and the narrower end ofthe body l0 preferably extends some distance beyond the fixed point l 3 as shown.

The pivoted lever Il, has at one end the tire tread engaging point 2i and at the opposite end thepointers 22 disposed at the opposite sides of the scale Ill and adapted to cooperate with the graduations provided upon each face of this scale. The lever Il as shown is made hollow to keep its Weight down and comprises the side walls 23 and 24' of plywood maintained in spaced relation to each other by the blocks 25, 26 and 2l. The lever Il is pivotally secured to the body I0 by the pivot pin 23 so that the longpointer arm portion of this lever is housed within the hollow body lli.

It is desirable that the tire measuring device of the present invention be provided with yielding means for normally holding the pointer 22 at the end of the scale I4 having the lower reading. This is accomplished in the construction shown by providing the spring steel blade 29 one end of which is rigidly secured within the pivot block 26 of the lever II and the other end of this spring rests upon the block 20. This serves yieldingly to hold the pointer 22 at the upper end of the scale so that the pointer may swing downwardly over the scale when the tire measuring device is placed upon the tread oi a tire as shown in Fig. 3 and is forced against the tire until the spaced points I2, I3 and 2I engage the tire tread. At this time the position the pointer 22 occupies with respect to the scale I4 will show accurately the diameter of the tire being measured. If desired the lever II may be formed with the hole 30 so that the measuring device may be hung on a nail when not in use.

As above stated the primary purpose of the present invention is to provide simple and practical means for determining whether or not dual tires are matched as to size. For example there is shown in Fig. 4 a truck or bus wheel 3I equipped with the dual tires 32 and 33, and as here shown the inner tire 32 is slightly larger than the outer tire 333, with the result that the inner tire at this moment is carrying the entire load as the outer tire does not contact the ground G. The fact that one dual tire is smaller than 'l the other can be easily detected with the tire measuring device of the present invention by placing this device upon one tire as shown in Fig. 3 or 4 to determine the tire diameter reading,

and then similarly determine the tire diameter reading of the other tire.

The proper graduation of the scale I4 may be worked out by geometry from the fact that the diameter of a circle can be determined if the angle is known that is subtended by two straight lines or cords of known length and which connect three points on the circumference of the circle. A simpler procedure for graduating the scale I4 is to draw circles on a flat surface having diameters ranging from 28 to 48 inches then place the measuring device shown in the drawing on the arc of each of these circles so that the 4 points I2, I3 and 2| will touch the arc and mark where the pointer 22 falls for each circle.

It will be seen from the foregoing that in order to use the measuring device of the present invention it is necessary to have access to only a small portion of the tire circumference, and that one person can easily and quickly check the diameter of the dual tires being used on a truck or bus wheel.

Having thus described my invention, what I claim and desire to protect by Letters Patent is:

A tire measuring device for determining the size of a vehicle tire by engaging three spaced points on its tread surface, comprising an elongated hollow body formed of two stiff at sheets secured in spaced relation to each other by several spacing blocks positioned therebetween and arranged to form two spaced fixed tread-engaging points, a at scale graduated to give tire size readings secured at one end of said body in equally spaced relation between said sheets, a lever that is considerably longer than said body and having a tread-engaging point at one end and two spaced pointers at its opposite end, and means for pivotally securing the lever to theopposite end of the body from that provided with the scale and in the space between said sheets so that its pointers straddle and move over the scale and its tread-engaging point projects beyond the body to engage the tread at some distance from said xed points. u

GERRITT VAN I. WESTON."

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 520,201 Bath May 22, 1894 825,911 Koch July 17, 1906 910,706 Monton Jan. 26, 1909 1,645,473 Cash Oct. l1, 1927 2,362,907 Levin Nov. 14, 1944 FOREIGN PATENTS Number Country Date 329,516 Great Britain May 22, 1930 

